Plant fibers and natural fillers can be obtained from forests, energy crops, agricultural staples, or agricultural residues in more than 1 billion tons annually. Plant fibers are being widely investigated for strengthening synthetic plastics including thermoplastic and thermoset polymers. The properties of plastics reinforced with natural fibers have a similar trend when compared with glass fibers, and therefore, represent an important commercial alternative for the fiber-plastic composites industry.
Fiber-plastic composites can be produced by a variety of techniques including thermoforming, vacuum forming, compression molding, extrusion, and injection molding. Plant fibers can substitute totally or partially glass fibers in many applications, and the cost of plant fibers is substantially less compared to glass fibers. For example, plant fibers cost approximately $US 0.20-0.25/lb while general purpose E-glass fiber costs approximately $US 2.00/lb. Natural fibers, such as dedicated crops (e.g., perennial grasses like miscanthus, switch grass etc.), cost around 10 cents/lb. Similarly, agri-residue natural fibers cost around 10 cents/lb.
The use of plant fibers in fiber plastic composites may have performance limitations. For example, composites containing thermoplastic polymers having dispersed organic reinforcing materials and/or fillers have been investigated. However, it is known by those versed in the art of manufacture of these materials that most plastics and plant fibers are chemically incompatible and are unsuitable for most practical applications.
Therefrom, there exists a need for composite materials, particularly those containing plastics and plant fibers and/or natural fillers, which have improved chemical, physical, and/or mechanical properties.
Therefore, it is an object of the present invention to provide methods of making and using composite materials, including hybrid composites containing plastics and natural fibers (e.g., plant fibers) as well as glass fiber, carbon fibers, or similar fibers, in combination with biochar and/or torrefied materials, which have improved functional performance. Moreover, the biomass source; biochar and/or plant fibers, may be modified chemically or physically or both to improve the interfacial adhesion, that is, silanes leading to the deposition of chemical species, alkaline treatments, and/or physical modifications including maceration and sieving, particle separation and selection, etc. may be applicable.